This invention relates to a process for decreasing or eliminating the sulphur as well as metal content of carbonaceous materials. The presence of sulphur and metals is the main factor that limits the use of carbonaceous materials, it then becomes necessary to develop industrializable techniques that reduce or eliminate such impurities.
The development of the radar during the second world war, estimulated the accelerated process of microwave technology. Research for industrial applications began in the mid 1940's, and included the treatment of carbon in order to remove the organic matter and the sulphur, the drying of feeding pasta, and the heating of frozen food.
Microwaves are electromagnetic energy. This form of radiation consists of the oscilation of the electric and magnetic fields that are perpendicular between them. Microwave energy is, generally, an ionized radiation that when becoming absorbed causes the molecular movement generating a quick and uniform heating. As opposed to ultraviolet, visible and infrared radiations whose frequency ranges cause the excitement of the valency electrons and of the molecular vibrations, the microwave radiation only causes dipolar rotation and ionic conduction. This phenomenon explains the fact that this kind of energy does not alter or destroy the molecular structure.
Kirkbride, Chalmer in their works (U.S. Pat. Nos. 4,123,230; 4,148,164 and 4,234,402), affirm that they satisfactorily desulphurate samples of bituminous carbon, previously crushed and dried, in contact with hydrogen at high pressures in a reactor of fluidizied bed. In a futuristic vision, Kirkbride patented, also in 1981 (U.S. Pat. No. 4,279,722) the use of microwaves in operations of petroleum refinement, given the fact that they would be working in operative conditions of less severity and in a shorter time span, therefore increasing the revenues and diminishing the costs.
Up to the present, the techniques proposed for the simultaneous demetallization and desulphuration suggest the catalytic hydrotreatment of heavy fractions of crude (U.S. Pat. Nos. 4,306,964; 4,447,314; 4,508,615; 4,510,043), or treating them with hydrogenic solvents in the presence of catalysts (U.S. Pat. Nos. 4,272,357 and 4,303,497). The process proposed on this patent, as oppossed to the processes previously mentioned, does not require severe conditions or catalysts, it is applicable to any carbonaceous material, the time of exposure is less than an hour, the percentages of extraction of sulphur as well as of metals are high, and it does not destroy the carbonic matrix of the material.
The objective of this invention is the simultaneous demetallization and desulphuration of carbonaceous materials using the advantages that microwave radiation offers over the methods of conventional heating.